Soap compositions



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United States Patent cc,

3,150,097 SOAP (IOMPOSITIONS William A. Kelly, Teaneck, N.J., assignor to Lever Brothers Company, New York, N.Y., a corporation of Maine No Drawing. Filed Apr. 18, 1961, Ser. No. 103,738 5 Claims. (Cl. 252-121) This invention relates to improved bar soap compositions adapted for use in hard water. More particularly, the invention is concerned with a bar soap composition containing an alkaline earth metal salt of a pentapropylenebenzenesulfonic acid as a lime soap dispersant.

One of the major disadvantages attending the use of soap bars is the water-insoluble precipitates which the soap forms with hardness ions present in hard water. The water-insoluble soap curd thus formed detracts from the detergent action of the bar and forms an unsightly scum on the surface of the Washing solution. On rinsing, the scum forms a deposit upon the skin and upon the containers employed for the washing operation, such as bathtubs, sinks and the like. The presence of this material is objectionable and in effect, results in incomplete cleaning.

The problem of preventing lime soap formation is a fairly complex one. When a water-soluble soap is added to hard water, the soap combines with calcium and magnesium ions and precipitates as a water-insoluble calcium and magnesium soap. As long as the concentration of soap in the solution remains above the foaming level, or if nonsoap detergents are present at a concentration suflicient to provide a foaming action, the water-insoluble lime soaps remain fairly well dispersed. However, when the solution is diluted as by rinsing to the extent that the foaming and dispersing power of the water-soluble soap and/or detergent disappears, the lime soaps precipitate to form a sticky and unsightly surface scum. In the usual washing process, the dilution is carried out with water containing additional hardness ions so that additional lime soaps may be formed. In addition to dilution, the precipitation of the lime soaps is dependent on the age of the soap solution and the violence of agitation, an increase of either encouraging lime soap formations.

The use of sodium and other alkali metal salts of alkyl aryl sulfonates to disperse lime soaps and improve lathering in hard water has been known for some time. Alkyl aryl sulfonate mixtures produced by sulfonating various petroleum fractions have been employed. In addition, alkaline earth metal alkyl aryl sulfonates, such as the magnesium salt, have been suggested for use as house hold detergents in the form of spray-dried compositions.

The prior art practice of employing sodium salts of alkyl aryl sulfonates in the formulation of a soap bar having lime soap dispersing properties is effective only where the sodium salt of the alkyl aryl sulfonate is employed at a relatively high level, i.e., in the order of 50--60%. In such case the mixtures are too sticky or tacky to process economically in the form of a bar. Although other workers in the field have suggested the use of starch to reduce the stickiness of such product, the difficulties have not been entirely overcome. The lather produced by soap bars containing the alkali metal alkyl aryl sulfonates is generally sticky and unpleasant to use.

It has now been found that firm soap bars containing an amount of alkyl aryl sulfonates sufilcient to impart useful lime dispersant properties thereto and which avoid the stickiness problem heretofore encountered in process- 3,150,097 Patented Sept. 22, 1964 ing are provided by combining a water-soluble soap with an alkaline earth metal salt of a pentapropylenebenzenesulfonic acid. Soap bars containing from about 10% to about 30% by weight of calcium or magnesium pentapropylenebenzenesulfonates of this invention have been found to provide soap bars of a firm and substantially nonsticky consistency. The pentapropylenebenzenesulfonic acid imparts lime soap dispersing properties imparted by sodium salts of alkyl aryl sulfonates employed at the same level. Furthermore, the lather produced by the soap bars is more voluminous and there are fewer difficulties encountered during the preparation or fabrication of these bars.

The alkaline earth metal salts of pentapropylenebenzenesulfonic acid employed according to this invention include the calcium and magnesium salts of sulfonates prepared from propylene polymers according to the method outlined in the Lewis Patent, U. S. No. 2,477,383. The alkane fraction employed in the preparation of thesesulfonates are those having an average carbon chain length of approximately 15.

The term pentapropylenebenzenesulfonate is used in this specification to describe mixtures comprising alkaline earth metal salts of a mixture of sulfonated monophenylsubstituted alkanes having an alkane structure corresponding to a mixture of acyclic polypropylenes, the acid form of the sulfonated mixture having an average molecular weight of between about 335 and about 370. Polypropylenebenzenesulfonate mixtures wherein about 20% of the alkyl portion has a carbon chain length of 15 and wherein a major part of the balance of the alkyl portion has chain lengths of 12, 13 14 and 16 carbon atoms are suitable according to this invention. Similarly, a polypropylenebenzenesulfonate mixture wherein nearly of the alkyl portion has a carbon chain length of 15 is suitable. The average molecular weight of the acid form of this sulfonate is about 368.

The alkaline earth metal salts of pentapropylenebenzenesulfonic acid of this invention are employed at a level of from about 10% to about 30%, the preferred level ranging from about 20% to 30% based upon the combined weight of the soap ond sulfonate present in the bar. Amounts of the sulfonate above about 30% increase the stickiness of the resulting soap bar to the extent that processing becomes difficult and the bar has a sticky feel. At levels below about 10%, insufficient improvement in the lime soap dispersing characteristics of the soap bar is obtained.

The term water-soluble soap employed in the specification and claims of this application is intended to include all of the water-soluble alkali metal soaps of fatty acids which are suitable for use in commercial soap bars. Normally the soap employed is a sodium or potassium soap or mixture thereof.

Commercial soaps are generally based upon mixtures of fatty acids obtained from various natural sources. Cocoanut oil, for example, is a material which has found considerable use in high quality hand soap products. Olive oil is often used as a source of fatty acids in making castile soap. Tallow is a constituent of many ordinary grade toilet soaps. All of these soaps are suitable for use in making the soap bars of this invention.

A typical soap bar may contain from 15 to 30% of a soap derived from cocoanut oil. The fatty acids of cocoanut oil comprise about 9% caprylic acid, 10% capric acid, 45% lauric acid, and 20% myristic acid. Thus, about 84% of the fatty acids found in cocoanut oil are those of relatively short (C to C chain length. It is Well known that the insoluble soaps formed from these fatty acids are more easily dispersible and therefore present much less of a problem in hard Water. Tallow soaps, on the other hand, consist mainly of stearic, oleic, and palmitic acids, and give rise to insoluble soaps which are much more difficult to disperse. Cocoanut oil soaps, or their equivalents, require a lower level of alkaline earth metal salt of pentapropylenebenzenesulfonic acid for effective lime soap dispersing action. Soaps which approximate the composition of cocoanut soap can be made from palm kernel oil, babassu oil and/or ucuhuba fat.

In addition to a water-soluble soap and an alkaline earth metal salt of pentapropylenebenzenesulfonic acid, the soap bars of this invention may contain various of the conventionally used additives, such as free fatty acids, perfume, pigments, preservatives, deodorants, and germicides.

As Will be demonstrated in the following examples, the magnesium and calcium salts of pentapropylenebenzene sulfonic acid provide a significantly improved lime soap dispersing effect at the relatively low levels, i.e., to 30%, required to provide the advantages of improved ease of processing over the corresponding sodium salts. Furthermore, the pentapropylene materials provide a decided advantage over the materials having an average carbon atom chain length of 12.

It is thought that the improved results obtained with the alkaline earth metal salts of pentapropylenebenzenesulfonic acid may be due to the superior foaming ability of these materials. The presence of the foam on the surface of the aqueous solutions containing them actually thins out the surface film of precipitated lime soaps and in some cases actually prevents its formation. In this respect, it is different from the sodium salts and the C sulfonate mixtures. 7

As discussed above, the molecular weight of the acid forms of the pentapropylenesulfonates of this invention should be between 335 and 370. Excellent results have been obtained with commercially available magnesium salts of alkylbenzene sulfonic acids, the acid forms of which have molecular weights of 349.7, 341, and 344.

The following examples illustrate several preferred embodimeuts of the invention.

EXAMPLE 1 A series of soap bars based on a soap stock containing 80% tallow soap and cocoanut oil soap were prepared containing lime soap dispersants at varying levels. The lime soap dispersants employed were the sodium salt of pentadecylbenzenesulfonate (Na PDBS), the sodium salt of dodecylbenzenesulfonate (Na DDBS), magnesium salt of pentadecylbenzenesulfonate (Mg PDBS), magnesium salt of dodecylbenzenesulfonate (Mg DDBS), and calcium pentadecylbenzenesulfonate (Ca PDBS). The dodecyland pentadecylbenzenesulfonates were prepared from polypropylene fractions as described in the Lewis patent, U.S. No. 2,477,383. Levels varying from 5 to based on the total weight of the soap bar were employed.

In preparing the soap bars, the ingredients were mixed with a suitable amount of water, chill-rolled, milled three times on a Day mill, plodded under vacuum and formed into bars having a moisture content of about 11% These bars were then evaluated according to the following procedures.

A. Cylinder Lathering Test Solutions of the soap bars being tested were made in Water containing 180 parts per million of hardness ions.

A concentration of 0.1% of the bar in the solution was employed since it was found that the maximum amount of lime soap was formed at this concentration. 100 ml.

of the soap solution Were placed in a 250ml. graduated completion of the agitation. The results of this test were as follows:

Dispersant Per- Total Volume 01 Solution and Suds cent Mg PDBS 5 ml no suds. Na DDBS 20 100 ml., no suds. Na PDBS 20 101 ml., slight suds on surface.

20 130 ml., very stable suds. 20 ml., fair suds on surface.

B. Hand Bowl Test Bars containing the various dispersants were tested by hand washing in bowls containing 180 parts per million hard water and 300 parts per million hard Water.

The

Dispersant Per- 180 p.p.m. 300 p.p.m.

cent

Na DDBS 20 Surface scum, poor Fair dispersion, better dispersion, no suds. than at 180 p.p.n1.,

, no suds.

Mg DDBS 20 Fair dispersion, better Good dispersion, no

, than sodium suds.

dodccyl, no suds.

Na PDBS 20 Fair dispersion, very Good dispersion, no

. slight surface curd, suds no suds.

Mg IDBS 20 Excellent dispersion, Excellent dispersion,

stable suds on stable suds on water. water.

Mg DDBS 30 Good dispersion, Excellent dispersion,

almost equal to 20% suds on water.

Mg PDBS, no suds.

Mg PDBS- 30 Excellent dispersion, Excellent dispersion,

suds on water. suds on water.

Mg PDBS 5 Poor dispersion, no Poor dispersion, no

suds. suds.

Tallow Igepon 20 Good dispersion, no Good dispersion, no

Ca PDBS 20 Excellent dispersion, Excellent dispersion,

stable suds. stable suds.

*A tallow methyl tauride sold by General Dyestufi Corporation.

C. Reflectance Test In this test, the lime soap formed in hard water solutions of soap bars containing the various dispersants is collected on black cloth, and the degree of lime soap formation is shown by measuring the reflectance of the cloth before and after the lime soap is collected. The following procedure was used.

A solution of the bar being tested was agitated in a Waring Blendor to producea volume of suds. 25 ml. of the suds were added to liter of Water containing 180 parts per million hardness parts of calcium ions and 60 parts of magnesium ions) and the Water stirred to quench the suds. The solution is then filtered through a black cloth and, after the cloth is dried, at reflectance measurement is taken using a Hunter reflectometer. The

following results were obtained:

v *A tallow methyl tauride sold by General Dycstutl Corporation.

These tests show the superiority of the magnesium and .calcium pentapropylenebenzenesulfonates in dispersing lime-soap scum and improving lather. Aside from these advantages, the magnesium and calcium salts also rendered the bars significantly less tacky or sticky than the sodium salts when used at the same level. The magnesium and calcium pentapropylenebenzenesulfonates also produced firmer bars than the sulfonates prepared from a C alkane fraction. Further, as evidenced above, the alkaline earth metal salts of pentapropylenebenzenesulfonic acid provide optimum results at a level considerably below the levels required of sodium salts and below the levels required for the C aryl sulfonates.

EXAMPLE 2 A series of soap bars based on a soap stock containing 80% tallow soap and 20% cocoanut oil soap were prepared containing sodium, magnesium and calcium salts of various polypropylenebenzenesulfonic acids. For convenience, the terms C C and C are used to define, respectively, benezenesulfonates prepared from polypropylenes having an average carbon chain length of 8, 12 and 15. The soap bars were made in five pound batches and were processed in a Readco mixer, a 3-mill, and a small plodder. Normal soap bar additives such as TiO and perfume were omitted. The bars contained approximately water.

The soap bars were evaluated by the Hand Bowl Test described in B. under Example 1 above. The results of this test were as follows:

ing of calcium and magnesium, the proportions based on the combined weight of the soap and the sulfonate.

2. The soap bar of claim 1 wherein the alkaline earth metal is magnesium.

3. A soap bar consisting essentially of about 65 parts by weight of a water-soluble soap selected from the group consisting of sodium and potassium tallow soap, about 20 parts by weight of a water-soluble soap: selected from the group consisting of sodium and potassium coconut soap and about 15% by weight of the magnesium salt of a mixture of sulfonated monophenyl-substituted alkanes having an alkane structure corresponding to a mixture of acyclic polypropylenes, the acid form of the sulfonated mixture having an average molecular weight of betweenabout 335 and about 370.

4. A method of dispersing water-insoluble salts of fatty acids of about 8 to about 18 carbon atoms formed in hard water solutions of water-soluble soaps selected from the group consisting of sodium and potassium salts of fatty acids having about 8 to about 18 carbon atoms, comprising the step of adding to said solutions at least about 10% based on the weight of soap and sulfonate of an alkaline earth metal salt of a mixture of sulfonated monophenyl-subs-tituted alkanes having an alkane structure corresponding to a mixture of acyclic polypropylenes, the acid form of the sulfonated mixture having an average molecular weight of between about 335 and about 370,

Level, per- Observations in water of hardness Sample Lime Soap Dlspersant cent by No. weight of bar 100 p.p.m. 180 ppm. 300 ppm.

NaC' benzene sultonate 20 Go Very good. Excellent. %g8 genzene sulgonagenn 2g 7 Very good..- Excellent.--" Excellent.

8 15 enzene su ona e Mgg 1benzene sulonae. iPoor Excellent- Mg 15 enzene su ona e. Mgg benzene sugonageflu Fair Excellent Mg 1 benzene su 011a e MgG benzene sulfonate 6. 7 Good Excellent OaC benzene su1fonate 20. 0 Very good- Exeellent Excellent. MgO benzene sultonate 20.0 Poor- Poor,

None (Control) V ry D 0 Very poo Very poor.

MgO1 benzene sultonate 59. 0 Excellent. Excellent. Excellent.

In hand lathering tests, each of the soaps described above lathered better than the control sample No. 8. The soap bar of sample 9 was extremely sticky and would be very difficult to process commercially.

It is to be understood that the foregoing examples are illustrative only and that modifications will occur to those skilled in the art. Therefore, the invention is not to be limited thereto but is to be defined by the appended claims.

I claim:

1. A soap bar consisting essentially of a water-soluble soap which normally forms water-insoluble soap curd in hard water selected from the group consisting of sodium and potassium salts of fatty acids of about 8 to about 18 carbon atoms and from about 10 to of an alkaline earth metal salt of a mixture of sulfonated monophenyl-substituted alkanes having an alkane structure corresponding to a mixture of acyclic polypropylenes, the acid form of the sulfonated mixture having an average molecular weight of between about 335 and about 370, the alkaline earth metal selected from the group consistthe alkaline earth metal selected from the group con- 45 sisting of calcium and magnesium, the amount of said alkaline earth metal salt being suflicient to disperse said Water-insoluble salts of fatty acids present in the solutions.

5. The method of claim 4 wherein the alkaline earth metal is magnesium.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE- CERTIFICATE OF CORRECTION Patent N00 3 l50 O97 September 22 1964 William A, Kelly It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

line 8 after "properties" insert which are Column 2 considerably superior to like properties line 4L2 for "0nd" read and column 5, line 22 for "3-mill' read 3-roll mill Signed and sealed this 2nd day of February 1965 (SEAL) Attest:

EDWARD J* BRENNER ERNEST W. SWIDER Commissioner of Patents Attesting Officer 

1. A SOAP BAR CONSISTING ESSENTIALLY OF A WATER-SOLUBLE SOAP WHICH NORMALLY FORMS WATER-INSOLUBLE SOAP CURD IN HARD WATER SELECTED FROM THE GROUP CONSISTING OF SODIUM AND POTASSIUM SALTS OF FATTY ACIS OF ABOUT 8 TO ABOUT 18 CARBON ATOMS AND FROM ABOUT 10 TO 30% OF AN ALKALINE EARTH METAL SALT OF A MIXTURE OF SULFONATED MONOPHENYL-SUBSTITUTED ALKANES HAVING AN ALKANE STRUCTURE CORRESPONDING TO A MIXTURE OF ACYCLIC POLYPROPYLENES, THE ACID FORM OF THE SULFONATED MIXTURE HAVING AN AVERAGE MOLECULAR WEIGHT OF BETWEEN ABOUT 335 AND ABOUT 370, THE ALKALINE EARTH METAL SELECTED FROM THE GROUP CONSISTING OF CALCIUM AND MAGNESIUM, THE PROPORTIONS BASED ON THE COMBINED WEIGHT OF THE SOAP AND THE SULFONATE. 